Process for the production of crimpable composite synthetic yarns



Apnl 18, 1967 E. LUZZATTO 3,315,021

PROCESS FOR THE PRODUCTION OF CRIMPABLE 00 OSITE TIC YARNS led 1965 SYN THE June 9,

NVENTQR Elite L 0 zzarfi United States Patent Office 2 Claims. (Cl. 264-168) This invention relates to a process for the production on a commercial scale of synthetic yarns exhibiting a sharp and marked crim-pability as a consequence of proper treatments. The invention is also concerned with the yams produced by putting said process into practice, more particularly composite-configuration yarns consisting of at least two polymers which are asymmetrically distributed throughout the yarn cross-section.

It is known that an urgent demand exists for crimped synthetic yarns. They, as is well known, possess valuable features of resilient shrinkability, covering power, bulk, thermal insulation, feel, optical effects and the like.

It is known, moreover, that, among said yarns, there are those in which the tendency towards and the capacity of crimping have a permanent nature, that is to say, yarns having, in cross-sectional configurations, geometrical and/ or constitutional asymmetry so that their tendency towards crimping is a consequence of the asymmetrical distribution of internal stresses in their own cross-sections.

A known method for the production of said yarns conpolymers through a polymeric component is encased and the other component. of different polymeric constitution and of ing different shrinkage and swelling properties, and by causing, during progress of spinning, an appreciable asymmetry in the distribution of the components in the crosssectional configuration of the extruded yarn, by heat treatment, the expected crimpability is obtained.

On account of the fact that, due to known phenomena of superficial tension and others, whose analysis and discussion are dispensed with as they are irrelevant to the ends of the invention and to the actual practice thereof, the filaments emitted by a single spinneret nozzle tend to take a cross-sectional shape of minimum periphery and circular cross-sectional shape. In practice the filaments produced by known methods exhibit markedly rounded off cross-sectional shapes, predominantly bean-like and ovular shapes, in which the innermost component is more-or less asymmetrically distributed. It is deemed unavoidable, in practice, that, upon extruding said composite yarns through a single spinneret nozzle of any optional configuration, cross-sectional shapes different from the circular shape cannot be obtained. Moreover, there result more pronounced asymmetrical distribution with more or less conspicuous misalignment of the different components in the cross-section of the composite yarn.

This places a sharp limitation on the crimping capacity and properties of the yarn, since such capacity and prop erties are a function of the asymmetry in the distribution of the differently shrinkable and swellable components in the composite yarn cross-section.

To circumvent this limitation it has been suggested that the two components of a composite yarn be distributed in side by side relationship, rather than the one internally of the other, but said suggestion entails the shortcoming of splitting apart of the two side-by-side components and this would be conducive to a poor cohesional resistance and would give rise to fraying of the individual components of the composite monofilamen-t.

3,315,021 Patented Apr. 18, 1967 In the light of the foregoing, the principal object of the present invention is to provide a novel method for the production of crimpable composite yarns having a crosssectional shape which is markedly different from circular, and in which the asymmetry in the distribution of the differently shrinkable or swellable components is developed to a much more intense degree than heretofore obtainable.

A further object of the present invention is to provide novel articles of manufacture consisting in composite yarns, capable of a crimp condition which is neater, more vigorous and more persistent than heretofore obtainable, said yarns including in their cross-section at least two geometrically sharply different portions which individually define areas of quite different internal constitution with respect to the shrinkability or swellability properties of the individual components.

Still another object of the present invention is to provide novel articles of manufacture formed by composite which combine maximum crimpability with maximum stability of the physical bond between the two components.

while providing a better and ampler degree of crimping.

Broadly, the invention exploits, in combination, the known possibility of extruding through a spinneret nozzle a composite yarn whose cross-section exhibits at least a peripheral portion and at least a core portion encased thereby, said core and said peripheral portion being formed tially melted state, merge into one another intimately and homogeneously to form a single monofilarnen-t which is preferably non-circular. The method according to the invention to provide a novel method for the production of yarns capable of acquiring, either directly or as a consequence of treatments ensuing their spinning, an energetic tendency towards crimping, which the application of critical and- The fact that the composite yarn according to the invention may be produced either by welding two or more filaments, individually fed out of distinct spinneret nozzles (if so, the welding takes place outside said spinneret, immediately and in close adjacence to the outlets of the capillary extrusion passageway) or by causing constitutionally different filaments to converge, in the innermost portions of their cross-sections, in a single extrusion passageway (if so, the welding takes place within said capillary passageway itself), does not change the basic idea of the invention.

Therefore, for the sake of clarity and uniformity of language, in the ensuing disclosure the term monofilaments will connote the threads, either homogeneous or of composite structure, extruded from individual spinneret nozzles, or converging and mutually welded in a single capillary outlet passageway, while the term strands will connote the structure resulting from the welding of said monofilaments, both downstream of, or within, the capillary extrusion passage. It is thus intended .to make conspicuous the fact that the monofilaments are welded together, downstream or upstream of the extrusion nozzlepassageway(s) before being thoroughly solidified and before taking the final cross-sectional shape which they will retain until drawn.

The term different constitution is intended to connote, in the ensuing disclosure, as well as in the appended claims, any possible form of differentiation which may be conducive to a different shrink or swell behavior and, consequently, also localized differentials in the internal stresses of the composite yarn. Said expression therefore is intended to comprise differences of molecular structure of the component polymers, and also of polymerization numbers, and physical differences stemming from spinning conditions which are conducive to the desired differences in magnitude and/or to conditions in which shrink or swell phenomena are brought about between said components in ensuing processing steps. Difference in molecular structure can derive from several factors: nature of the monomers, their proportions, presence of additives, polymerization conditions, treatments which give rise to or hinder branching-offs and molecular reticulations, et-c.

According to one embodiment of the invention, the composite yarn is produced by extruding, through at least two nozzles placed side by side, at least a homogeneous monofilament of a first synthetic component and at least a composite monofilament having an outer portion or sheath formed by said first component and an inner core formed by at least a second component of a different constitution.

According to another embodiment of the invention, composite monofilaments, having outer portions of equal constitution and inner portions of a constitution different from that of the outer portions and different from one another, are extruded through at least two nozzles placed in side by-side relationship.

In both cases, the perfect weldability of the monofilaments is ensured by the identity (or at least a close aflinity) of the outer components of the monofilaments intended to come into mutual contact when coming out of the nozzles of the multiple spinneret. The marked deviation from the circular shape of the final cross-section of the strands is ensured by the welding of a plurality of monofilaments. The sharp asymmetry in the distribution of different components in the cross-section of the final strand is ensured by the difference between the componentswhich are present within the monofilaments, which form neatly individualized and spaced apart portions in the final strand. The high crimpability is, eventually, due to the ensuing happy combination of the differentiation condition of the components along with the sharp asymmetry with which said constitutionally different components are distributed in the strands final cross-section.

Preferably, but not necessarily, the composite monofilaments have a concentric structure. The production of a composite monofilament having a non-concentric structure is much more complicated owing to the necessity of determining and controlling the degree of eccentricity. While said complication was imperative with the known art in order that crimpable strands might be obtained having one component external to the other, the present invention has made it superfluous.

The device for practicing said first embodiment of the inventive process comprises, for the formation of each strand, at least two spinneret nozzles, one at least of which is adapted to extrude a composite monofilament, in which either component is arranged internally of the other'one. In the ensuing disclosure, the inner component will be dubbed core and the outer component, sheath. Said device, therefore, comprises means for feeding a stream of a melted polymer intended to form the core, to each nozzle within a stream of a melted polymer intended to form the sheath, and means for feeding said latter polymer in the outer portion and in the entirety of the cross-sectional area of one or more spinneret nozzles adjacent to the one mentioned above, said adjacent nozzles being capable, in turn, of extruding composite monofilaments.

According to a preferred embodiment of the invention, the device comprises a spinneret plate having at least two adjacent nozzles for each strand to be extruded, and at least two wells for feeding the melted polymer, along with ducts for putting one or more wells in communication with both said nozzles and the other well with either nozzle only. One feeding well may have, a cylindrical con-figuration, and another an annular configuration surrounding the first well. The wells are able to feed a plurality of pairs of spinneret nozzles, said pairs being in a number equal to that of the strands to be extruded and equi-angularly spaced concentrically with said wells.

Said device can be readily modified to suit the extrusion of strands comprising more than one composite monofilament and/ or of more than two monofilaments.

The device for putting into practice another embodiment of the invention, by welding the monofilaments before extruding the melted material comprises, for the formation of each strand, a spinneret nozzle forming the outlet of a short extrusion capillary passageway in which two separate passageways are caused to converge, one at least of which is adapted to the formation of a composite monofilament wherein either component is arranged internally 0f the other, so as to obtain in said passageway a flow in which both the inner component or core and the outer component or sheath are present. The distribution conditions of the two different components are preserved down to the intake of the capillary extrusion passageway, -in which the inner component is welded to the outer component or to the outer fraction of the homogeneous monofilament coming from the other feeding passageway, for the formation of the markedly asymmetrical composite strand which is thus extruded through said capillary passageway.

The conditions of strong asymmetry which are conducive to the desired crimpability features of the strands produced according to said alternative method, can be improved by forming said capillary passageway with an elongate or otherwise shaped cross-section so that the components whose flows are combined within said passageway may take, therewithin, an essentially side-by-side mutual relationship.

More particularly, it should be borne in mind that, in order that favourable proper-ties for the composite strand might be obtained, it is necessary to adjust, every time, the ratios of the portions of the strands cross-sectional area respectively occupied by the two or more components.

In the two-component case, the strands cross-sectional area may comprise 25% of one component, or less and correspondingly, 75% of the other component or even a) more, but in the majority of the instances it is preferred that the component which occupies the least portion of the cross-sectional area be present for at least 40% by volume, very favourable results being obtained, in many instances, with proportions of from 45 %55% to 5070- 50% of the components.

On the other hand, the sheath should not be exceedingly thin in the composite monofilaments. Although composite monofilaments, having a very thin sheath or even a sheath which does not enclose the core completely (it being enough that the sheath is present in the area in which the interfilament welding in the same strand is intended to take place), come within the scope of the present invention, it is however preferred that, in each composite monofilament, the sheath occupies not less than and preferably at least the of the cross-section. It is apparent that, under such circumstances, it would be awkward to arrive at a composite strand in which the two components are in equal proportions or very nearly so, particularly should the nozzles corresponding to the several monofilaments be identical.

In theory, the polymers can be fed from the several nozzles under different pressure and velocity conditions, but this would entail noticeable complications. It is preferable to act upon the form and the cross-section of the nozzle. In the light of this, nozzles are constructed having different cross-sections both with respect to shape and also to size, so as to control in the desired manner the structure of the monofilaments and the degree of eccentricity of the different polymeric portions without giving rise to exceedingly highly differences in the quantities thereof.

For example, it is advantageous to associate a composite monofilament having a circular cross-sectional shape and a core-sheath structure with a solid monofilament having an elongate, e.g. rectangular, cross-sectional shape and a cross-sectional area such as to determine, concurrently with the sheath area, the desired proportion of the polymer which forms said solid monofilament and said sheath.

Many changes are possible in this way for obtaining optimum cross-sections.

A detailed description follows of exemplary embodiments of the invention, with reference to the accompanying drawings in which there are shown on a greatly enlarged scale, a few possible shapes of strands and of means adapted for their extrusion, the particular specific compositions of said strands being, in turn, susceptible of being different and of being differently combined as will be explained hereinafter.

In the drawing:

FIGURE 1 shows, in cross-section and on a greatly enlarged scale, a strand produced according to one embodiment of the invention and formed by the union of two monofilaments having an originally circular crosssection and similar diameters, one monofilament only having different components and a core-sheath structure.

FIGURE 2 similarly shows a strand formed by uniting circular monofilaments, both having a core-sheath structure but having, respectively, cores of different composition.

FIGURE 3 shows a strand in which the asymmetry conditions are due to the combined effects of constitutional asymmetry and the cross-sectional structure of the monofilaments.

FIGURE 4 shows a strand formed by welding three monofilaments together, these being oriented so as to obtain a condition of marked geometrical asymmetry.

FIGURES 5 and 6 represent, in diametrical cross-sectional View, and in axial view from the bottom, respectively, and in structurally simplified outline with dimensional values purposely altered so as to give a clear picture of essential details, more particularly of the feeding and extrusion passageway, a multiple spinneret which can be utilized for the simultaneous formation of strands of the kind shown in FIG. 1 or FIG. 3.

FIGURE 7 is a detail on an enlarged scale of one extrusion unit of the spinneret of FIG. 5.

FIGURE 8 shows, in a greatly magnified cross-sectional view, a composite strand obtained according to another embodiment of the invention.

FIGURE 9 shows an extrusion unit for the formation of a filament such as that of FIG. 8.

Having reference to the drawings, it is noted that the strands of FIGS. 1, 3 and 4 are formed by two compoand of the homogeneous monofilaments. The strand of FIG. 2, conversely, is formed by three components, both monofilaments having a core-sheath structure, the components A and A" forming the cores of the two monofilaments and the components B of the two sheaths being welded together. Having now reference to FIGS. 5 and later, and a feeding body 11, connected to the plate 10 in any suitable way, egg. by a threaded sleeve 12. Body 11 is fitted with several feeding wells. The central well 13 is for feeding in the polymer B and the outer annular well 14 is for feeding in the component A. The spinneret is adapted, for example, to the production of strands such as shown FIG. 1. The well 13 feeds through suitable passages 15 a recess 16 between the plate 10 and the body 11. The annular well 14, feeds nozzles 17 equal in number to the extruded strands. Every one of the nozzles 17 is placed in registry with a spinneret nozzle 18 from which a composite monofilament is to be extruded.

ployecl for extruding composite strands. nozzle 18 there is a nozzle 19.

The two wells 13 and 14 are naturally fed with the polymers A and B in melted form and are suitably filtered and subjected to the desired extrusion pressure, with known means.

For the production of strands of the kind depicted on FIG. 1, both the extrusion component A", or A, in the axis of the passage which feeds the extrusion capillary 19. Said embodiment is not shown since, in practice, it is a repetition or duplication of the above described means the composite monofilament through the extrusion nozzle 18.

For the production of a strand of the kind shown in F1 4, the spinneret will be equipped, for each spinning unit, with three capillary nozzles, one of which corresponds to the nozzle 18, for the formation of the central core-sheath portion of the strand, and with two additional nozzles of the kind indicated at 19, but having a suitable cross-sectional area and with the required orientation with respect to the first-named nozzle 18.

Said alternative embodiments are not described since they can be made by applying current knowledge in the art.

For the formation of a strand of the kind shown in FIG. 8, or equivalent, by welding the monofilament within the said extrusion capillary, a spinneret structurally akin to the one described above can be used, but comprising, for each spinning unit (i.e. for the formation of each individual strand), a single capillary nozzle 20 (FIG. 9) provided on the internal face of the foraminous plate 10' and in which converge two separate passageways 21 and 22, each fed with the component B; e.g. through a pocket 16' corresponding to the pocket 16 described above between said plate 10 and the feeding body 11'.

Through suitably shaped and oriented nozzles and passageways 23, the component A is injected into the component B which flows through the passage 21 so that within the latter a flow of melted material takes place, whise internal component is the component A and this is externally coated by the component B. The components in the flowing stream travel along the passageway 21 and the composite is not substantially altered when the same is combined with the flow of the B component only, coming from the passageway 22. The capillary extrusion nozzle 20 will preferably have an elongate, elliptical, rectangular or other shape so as to encourage the welding between the two flows coming from the passageways 21 and 22 without substantially altering the distribution of the two components in the cross-sectional configuration of the resultant strand.

Similarly, strands can .be produced which comprise two cores different from one another, analogously with what has been described with reference to FIG. 2, by forming a nozzle and an injection passageway of the kind indicated at 23, also in registry with the second passageway 22 and by feeding two different components into said two injection nozzles as indicated by A and A" in FIG. 2.

Numerous synthetic materials are usable in putting the invention into practice. The inventive method can be applied to the melt-spinnable polymers, as well as to the dry-spinnable polymers and possibly also to the wetspinnable polymers, the means for obtaining composite monofilaments from all these kinds of yarns being known in the art. Among the melt-spinnable yarns, polyamides, polyesters and polyolephines are particularly important. Among the polyamides there can be cited the hexamethylenediammonium adipate polymer (nylon 66), the aminocaproni-c acid and caprolactam polymer (nylon 6), the copolymers of terephthalic acid and adipic acid with hexamethylenediamine or of sebacic and adipic acid with hexamethylenediamine, the copolymers of adipic acid and hexamethylenediamine and caprolactam, the polymer of metaxylilenediammonium adipate etc.

Among the polyesters particular mention is deserved by polyethylene terephthalate and the polyterephthalates of other glycols, for example aromatic glycols, and also the polymers modified with sulphonic groupings or containing additives capable of increasing the viscosity of the melt. Among polyolephines, .polyethylene, polypropylene and their copolymers should be mentioned.

Among the dry-spinnable, or wet-spinnable filaments particular mention is deserved by polymers or copolymers of acrylonitrile and polyvinyl chloride. The several polymers can be combined by employing one of them to form the core, and the other one the sheath of the composite monofilaments, or by inverting their structural ratio. Also strands can be subjected to thermostabilization processes to obtain or enhance the desired differential properties of shrinkability and/or swellability.

The polymers can be modified by introducing acidic or alkaline groupings therein.

A few particular examples of spinning particular strands according to the invention will be given below by way of illustration.

Example 1 Through a spinneret as illustrated in FIGS. 5 and 7, wherein the spinneret nozzles are circular, strands are spun having a cross-section such as shown in FIG. 1 and having the following characteristics. The core A consists of ethylene polyterephthalate having an intrinsic viscosity of 0.6 in a phenol-tetrachlorethane 60-40 mixture, and the sheath and the homogeneous monofilament B are formed by polycaprolactam having an intrinsic viscosity of 0.98 in metacresol.

The total denier count of the strands is 4 den. and the polyamide component occupies 60% of the whole crosssection of the strand. After having cooled in air the extruded strands, as usual, and after having taken them up on a spool, they are cold-drawn with a draw ratio of 3.5. The strand obtained has a very good crimpability both when heat-treated, for example "in boiling water and in shanks, i.e. in a tensionless state.

Example 2 A composite strand is prepared according to Example 1 but by employing in lieu of polycaprolactam a polyadipate of hexamethylenediammonium having an intrinsic viscosity of 1.03. The strand, after having been drawn with a ratio of 3.5 is wound up on a spool and oven treated at a temperature of C. in an inert gas atmosphere for 30 minutes. The strands thus obtained have a potential crimp which can be unfolded by thermally treating the strands as in Example 1.

Example 3 The same components as in Example 2 are spun through a spinneret having nozzles adapted to the formation of a strand according to FIG. 3 and in which the nozzles have the same construction. The treatment is the one of Example 2.

The denier count of each composite strand is 4 den. and the volume ratio of polyamide to polyester is 60%:40%

Example 4 The same components as in the preceding example are extruded through a spinneret having a circular nozzle and a rectangular nozzle, in which the ratio of the longer side to the shorter one is 3 to 1, and the total area is two thirds of the area of the circular nozzle. Strands having an overall denier count of 3.5 are obtained and in which the ration of the two components is nearly 50-50.

Example 5 Through a spinneret there is extruded a composite strand of the kind shown in FIG. 4 and in which the core of the composite monofilament is formed by the same polyethylene terephthalate of Example 1, while the sheath of the composite monofilament and the homogeneous monofilaments are formed by the polycapronamide of Example 1.

The treatment is as in Example 1.

Example 6 Through a spinneret formed as in FIGS. 5 and 7 but modified by the introduction of a second annular Well in communication with a nozzle of the body 11 which feeds the axial zone of the nozzle 19, is extruded a composite strand of the kind shown in FIG. 2, in which the core A consists of polypropylene and the core A" consists of ethylene polyterephthalate, while the portion B is formed by polycapronamide.

The treatment is that of Example 2.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method for producing crimped synthetic textile fibers, comprising the steps of feeding two streams of a molten first synthetic high molecular weight fiber-forming polymer simultaneously into and through two adjacent spinneret passageways, of feeding a stream of a molten second high molecular weight polymer centrally and axially of one of the said two streams in one of said passageways and concurrently therewith, to cause a compound stream of molten polymer filamentary structure to issue from said one passageway, consisting of an outer portion of said first polymer and of a core portion of said second polymer, said core portion being coaxial of said outer portion, the remaining stream of said molten first polymer issuing as a one component filamentary structure from the other passageway adjacent said compound filamentary structure, whereby the one component filamentary structure and the two component filamentary structure become fused after passing through the passageways of the spinneret to provide a compound unitary filament having an elongated cross-sectional shape and wherein said second polymer is asymmetrically located, and promoting permanent crimp in said compound filament by heat processing the same to cause a differing longitudinal contraction in said first and second polymer portions.

2. A method for producing crimped synthetic textile fibers, comprising the steps of feeding two streams of a molten first synthetic high molecular weight fiber-forming polymer simultaneously into and through first and second adjacently located spinneret passageway, of feeding a stream of a molten second high molecular weight polymer centrally and axially of the stream of said first polymer in said first passageway and concurrently therewith, to provide a first compound filamentary structure having an outer portion of said first polymer and a core portion of said second polymer, said core portion being coaxial of said outer portion, of feeding a stream of a molten third high molecular weight polymer centrally and axially of the stream of said first polymer in said second passageway and concurrently therewith, to provide a second compound filamentary structure having an outer portion of said first polymer and a coaxial core portion of said third polymer, said two compound filamentary structures becoming fused together as they issue from said passageways after passing through the spinneret to provide a compound unitary filament of elongate crosssectional shape having a plane of symmetry and wherein the core portions of said second and said third polymers are oppositely located with respect to said plane, and of promoting permanent crimp in said filament by heat processing to cause differing longitudinal contraction in the core portions formed of said second and third polymers.

References Cited by the Examiner ALEXANDER H. BRODMERKEL,

Primary Examiner.

A. L. LEAVITT, J. H. WOO, Assistant Examiners. 

1. A METHOD FOR PRODUCING CRIMPED SYNTHETIC TEXTILE FIBERS, COMPRISING THE STEPS OF FEEDING TWO STREAMS OF A MOLTEN FIRST SYNTHETIC HIGH MOLECULAR WEIGHT FIBER-FORMING POLYMER SIMULTANEOUSLY INTO AND THROUGH TWO ADJACENT SPINNERET PASSAGEWAYS, OF FEEDING A STREAM OF A MOLTEN SECOND HIGH MOLECULAR WEIGHT POLYMER CENTRALLY AND AXIALLY OF ONE OF THE SAID TWO STREAMS IN ONE OF SAID PASSAGEWAYS AND CONCURRENTLY THEREWITH, TO CAUSE A COMPOUND STREAM OF MOLTEN POLYMER FILAMENTARY STRUCTURE TO ISSUE FROM SAID ONE PASSAGEWAY, CONSISTING OF AN OUTER PORTION OF SAID FIRST POLYMER AND OF A CORE PORTION OF SAID SECOND POLYMER, SAID CORE PORTION BEING COAXIAL OF SAID OUTER PORTION, THE REMAINING STREAM OF SAID MOLTEN FIRST POLYMER ISSUING AS A ONE COMPONENT FILAMENTARY STRUCTURE FROM THE OTHER PASSAGEWAY ADJACENT SAID COMPOUND FILAMENTARY STRUCTURE, WHEREBY THE ONE COMPONENT FILAMENTARY STRUCTURE AND THE TWO COMPONENT FILAMENTARY STRUCTURE BECOME FUSED AFTER PASSING THROUGH THE PASSAGEWAYS OF THE SPINNERET TO PROVIDE A COMPOUND UNITARY FILAMENT HAVING AN ELONGATED CROSS-SECTIONAL SHAPE AND WHEREIN SAID SECOND POLYMER IS ASSYMMETRICALLY LOCATED, AND PROMOTING PERMANENT CRIMP IN SAID COMPOUND FILAMENT BY HEAT PROCESSING THE SAME TO CAUSE A DIFFERING LONGITUDINAL CONTRACTION IN SAID FIRST AND SECOND POLYMER PORTIONS. 